Shewanella oneidensis grows on biochar as an electron acceptor via direct contact without flavins
- 1University of Delaware
Abstract
Pyrogenic black carbon, such as biochar and wildfire char, possesses a reversible electron storage capacity (ESC), allowing it to serve as an electron donor or acceptor for microorganisms. However, not all the ESC is bioavailable, and the proportion available varies by culture. We hypothesized microbes capable of producing soluble redox mediators could access the ESC in biochar interior and thus utilize a higher percentage of the ESC than organisms without a mediator. To test this hypothesis, we grew wild-type Shewanella oneidensis (MR-1) and {Delta}bfe MR-1, a mutant incapable of exporting flavins, on air-oxidized wood biochar. Cell counts and redox titration show that both strains of MR-1 grew to similar cell densities and accessed comparable amounts of biochar ESC (~19%). The addition of exogenous flavin mononucleotide (FMN) yielded no measurable increase in final cell density, due to the strong adsorption of FMN to biochar. SEM images show attachment of MR-1 and {Delta}bfe to biochar surfaces and the presence of nanowires. This study demonstrates MR-1 can utilize biochar ESC for growth, through direct physical contact without the involvement of flavins. Understanding how microbes metabolize biochar provides insight into the impacts and biogeochemical roles of pyrogenic carbon.
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BibTeX
@misc{singh2026shewanella,
title = {{Shewanella oneidensis grows on biochar as an electron acceptor via direct contact without flavins}},
author = {A. Singh and J. L. Keffer and J. Choi and P. C. Chiu and C. S. Chan},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.21.753187},
url = {https://www.biorxiv.org/content/10.64898/2026.09.21.753187v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Shewanella oneidensis grows on biochar as an electron acceptor via direct contact without flavins
AU - A. Singh
AU - J. L. Keffer
AU - J. Choi
AU - P. C. Chiu
AU - C. S. Chan
PY - 2026
DA - 2026/09/21
PB - bioRxiv
DO - 10.64898/2026.09.21.753187
UR - https://www.biorxiv.org/content/10.64898/2026.09.21.753187v1
AB - Pyrogenic black carbon, such as biochar and wildfire char, possesses a reversible electron storage capacity (ESC), allowing it to serve as an electron donor or acceptor for microorganisms. However, not all the ESC is bioavailable, and the proportion available varies by culture. We hypothesized microbes capable of producing soluble redox mediators could access the ESC in biochar interior and thus utilize a higher percentage of the ESC than organisms without a mediator. To test this hypothesis, we grew wild-type Shewanella oneidensis (MR-1) and {Delta}bfe MR-1, a mutant incapable of exporting flavins, on air-oxidized wood biochar. Cell counts and redox titration show that both strains of MR-1 grew to similar cell densities and accessed comparable amounts of biochar ESC (~19%). The addition of exogenous flavin mononucleotide (FMN) yielded no measurable increase in final cell density, due to the strong adsorption of FMN to biochar. SEM images show attachment of MR-1 and {Delta}bfe to biochar surfaces and the presence of nanowires. This study demonstrates MR-1 can utilize biochar ESC for growth, through direct physical contact without the involvement of flavins. Understanding how microbes metabolize biochar provides insight into the impacts and biogeochemical roles of pyrogenic carbon.
ER -